Respiratory System
The initial respiratory response to cold stress is a significant increase in rate (ie, hyperventilation) followed by a decrease (ie, hypoventilation) (see Exhibit 11-2). Skin temperature afferents can influence respiratory function dramatically. Certain individuals will hyperventilate when they are exposed to a cold stress and others will not. The cold-stressed hyperventilation is followed by a progressive decrease in the respiratory minute volume that is proportional to the decreasing metabolism. The control of respiration becomes compromised as the function of the brain stem is impaired by severe hypothermia Respiratory rate falls from 15 to 7 breaths per minute at 30oc to 7 to 4 breaths per minute at temperatures in the mid 20s. Eventually, retention of carbon dioxide by the tissue leads to respiratory acidosis. In most cases of severe hypothermia respiration diminishes and the heart continues to contract for some time.